Max Planck Institute for Astronomy
"How Gas Forms Stars: The Influence of Galaxy Dynamics"
Abstract: The nature of star formation is one of the prevailing issues in modern astronomy. I will describe how the way we interpret this process is changing, enabled by high-resolution observations of nearby galaxies and new insights in to the role of galaxy dynamics. Gas motions on large scales in galaxies affect its organization and structuring all the way down to the seeds of star formation, giant molecular clouds (GMCs). New evidence suggests that GMCs inherit their properties from their surroundings; they are not isolated entities, dynamically decoupled from their environment. This sensitivity to environment challenges the idea behind a 'universal' GMC that lies at the heart of standard theories of star formation. I will describe how gas motions driven by non-axisymmetric bar/spiral instabilities mediate the link between a cloud and its surroundings and thus determine its ability to collapse and form stars. The result is that very specific patterns in global star formation are introduced within galaxies, with the rate at which gas is transformed into stars varying by up to an order of magnitude. This impact of gas motions on star formation activity affects our understanding of disk formation across cosmic time.